# How to convert video to MP3: extract audio from an MP4, pick the bitrate, and know the file size before you start

> A lecture you want to listen to on a walk, an interview to share as audio, a clip from your own video. Here is how to pull the sound out of a video on your phone or laptop, which bitrate to choose, how big the MP3 will be, and why very long files can fail.

Published 2026-10-23 by Toolcloak. 5 minute read. Original: https://toolcloak.com/articles/how-to-convert-video-to-mp3-extract-audio-from-an-mp4-pick-the-bitrate-and-know-the-file-size-before-you-start
Related free tool: [Video to MP3 Converter](https://toolcloak.com/tools/video-to-mp3)

Plenty of video is really audio with a picture attached: a lecture, a podcast recorded on camera, a speech, a family function you want to hear again, a song you filmed yourself. Carrying the whole video around wastes space and data. An MP3 of the same thing is a fraction of the size and plays anywhere, even with the screen off. This guide shows how to get the audio out, what the settings mean, and how to avoid the few things that go wrong.

> **In short**
> - Choose a video (or audio) file in [Video to MP3](https://toolcloak.com/tools/video-to-mp3), pick a quality, and press **Convert to MP3**.
> - Quality options are **64, 128, 192 and 320 kbps**. File size follows the number: 128 kbps is about **1 MB per minute**.
> - Everything runs **on your device**. The file is not uploaded, and there is a limit of **400 MB** per file.
> - It works on files already on your phone or computer. It does **not** download from a web link.
> - Use it only for audio you own or have permission to use.

## How to convert a video to MP3, step by step

1. Open the [Video to MP3](https://toolcloak.com/tools/video-to-mp3) tool.
2. Tap the box and choose a video, such as an MP4, WEBM or MOV. An audio file such as WAV or M4A also works.
3. Pick **MP3 quality**. Leave it at 128 kbps if you are unsure.
4. Press **Convert to MP3**. A progress bar shows the encoding.
5. When it finishes, press play on the preview to check it, then download. The file keeps the video’s name with .mp3 on the end.

Try it: [Video to MP3 Converter](https://toolcloak.com/tools/video-to-mp3). Choose a video, pick the quality, and press Convert to MP3.

**What happens inside your browser**

1. **Reads the sound.** The audio track is decoded from your video **on your device**.
2. **Sets the sample rate.** Common rates are kept. Anything higher than 48,000 Hz, or unusual, is brought to 44,100 Hz.
3. **Encodes the MP3.** The sound is compressed at the **kbps** you picked.
4. **Gives you the file.** A preview player and a download button appear.

*No video is sent to a server at any point, so private recordings stay private.*

## Which bitrate should you choose?

Bitrate, shown in kbps (kilobits per second), is how much data is spent on each second of sound. More data means more detail, and a bigger file. The tool gives you four choices.

**MP3 quality, from small to best**

| Zone | From | To |
| --- | --- | --- |
| 64 kbps | 0 | 96 |
| 128 kbps | 96 | 160 |
| 192 kbps | 160 | 256 |
| 320 kbps | 256 | 320 |

*The zones show which setting suits which job. They are rough guides, not hard edges.*

| Kind of audio | Good choice | Why |
| --- | --- | --- |
| Lecture, interview, voice note, sermon | 64 or 128 kbps | Voices stay clear at low bitrates, and files stay small for a long recording |
| Podcast or a mix of talk and music | 128 kbps | A safe middle for most listening |
| Songs from your own video | 192 or 320 kbps | Music has more detail, so it benefits from more data |
| You plan to edit it later | 320 kbps, or use the [Video to Audio Extractor](/tools/video-to-audio-extractor) | Less loss. The extractor makes a WAV, which keeps every detail but is much bigger |

> **A higher number cannot add what was never there:** If the video’s own sound was recorded at modest quality, choosing 320 kbps will not improve it. It only makes a bigger file. MP3 is also a lossy format, so turning compressed video audio into MP3 loses a little each time. For music, pick 192 or 320 so the second round of compression stays gentle.

## How big will the MP3 be?

The tool encodes at a steady bitrate, so size is simple arithmetic: kilobits per second times seconds, divided by 8 to get kilobytes. That is why you can know the size before you start.

**MP3 size by length and quality**

| Length | 64 kbps | 128 kbps | 192 kbps | 320 kbps |
| --- | --- | --- | --- | --- |
| 3-minute song | 1.4 MB | 2.9 MB | 4.3 MB | 7.2 MB |
| 10 minutes | 4.8 MB | 9.6 MB | 14.4 MB | 24 MB |
| 30 minutes | 14.4 MB | 28.8 MB | 43.2 MB | 72 MB |
| 1 hour | 28.8 MB | 57.6 MB | 86.4 MB | 144 MB |

Compare that with the video you started from. A 10-minute phone video can easily be hundreds of megabytes, while its sound alone is under 10 MB. If the video itself is what needs to be smaller, read [how to compress a video](https://toolcloak.com/articles/how-to-compress-a-video-for-whatsapp-or-email-resolution-bitrate-and-file-size-explained).

About the **Mono** switch: its label hints at a smaller file, but at a steady bitrate the size is set by the kbps you choose, not by the number of channels. What mono does is mix both channels into one and give the whole bitrate to it, which suits speech. To make a file smaller, lower the kbps instead.

## Why very long videos can fail

To turn a video into MP3, the browser first unpacks the audio into raw sound, and raw sound takes far more room than the compressed file does. Stereo at 44,100 Hz uses about **21 MB for every minute** while it is being worked on, and the tool makes a few working copies along the way. A phone has much less memory to spare than a laptop.

**Memory needed for the unpacked audio alone (stereo, 44.1 kHz)**

|  | Value |
| --- | --- |
| 3 min | 64 |
| 10 min | 212 |
| 30 min | 635 |
| 1 hour | 1,270 |

*These are rough figures for the unpacked sound before any copies are made. A file over 400 MB is refused outright. Shorter pieces are far safer.*

- **Cut long recordings first.** Use the [Video Trimmer](https://toolcloak.com/tools/video-trimmer) to keep just the part you want, or the [Audio Cutter](https://toolcloak.com/tools/audio-cutter) once you have the MP3.
- **Close other tabs** before you start, especially on a phone.
- **If it stops**, try a smaller piece. A two-hour lecture is better handled as two one-hour files.
- **If it says it could not read the file**, the video may use a format your browser does not handle, such as some MKV or AVI files. Try an MP4, or Chrome or Edge on a laptop.

## What this tool does not do

- **It does not download from a link.** The file must already be on your device. Paste-a-link converters have to fetch the video for you, which is a different service with different rules.
- **It does not remove copyright.** Make MP3s only from video you made, own or have permission to use, such as your own recordings, your own lectures or content that is licensed for it.
- **It does not edit the sound.** Volume changes, joining and trimming have their own tools, such as the [Audio Compressor](https://toolcloak.com/tools/audio-compressor) and the [Audio Joiner](https://toolcloak.com/tools/audio-joiner).

## Common jobs, and the settings that suit them

**Pick by the job**

| Box | What it means |
| --- | --- |
| Lecture for the commute | Mono or stereo, **64 kbps** is plenty and a one-hour lecture is only about 29 MB. |
| Interview or call recording | **128 kbps** keeps voices natural and the file easy to send. |
| Your own song or performance | **320 kbps** if you can spare the space. Keep the original video too. |
| Voice note from a video message | **64 kbps** is more than enough, and small files share quickly. |

*If you will send the MP3 by WhatsApp or email, remember that smaller files upload faster on a slow connection.*

Once you have the MP3, the usual next steps are trimming it with the [Audio Cutter](https://toolcloak.com/tools/audio-cutter) or joining several clips with the [Audio Joiner](https://toolcloak.com/tools/audio-joiner). For file sizes in general, our explainer on [KB, MB and why 1 TB shows as 931 GB](https://toolcloak.com/articles/why-a-1-tb-drive-shows-931-gb-kb-kib-mb-and-mbps-explained) clears up the units.

## Frequently asked questions

### How do I convert a video to MP3?

Open the Video to MP3 tool, choose your video, pick a quality such as 128 kbps and press Convert to MP3. Play the preview, then download the file. It runs on your device and the video is not uploaded.

### video se mp3 kaise banaye?

Video to MP3 tool kholiye, apni video file chuniye, quality chuniye jaise 128 kbps aur Convert to MP3 dabaiye. Preview sunkar MP3 download kar lijiye. Video kisi server par upload nahi hoti.

### Which MP3 quality should I choose?

Use 64 kbps for speech, 128 kbps as a standard choice, and 192 or 320 kbps for music. A higher number makes a bigger file and cannot add detail that the original sound did not have.

### How big is an MP3 per minute?

At 128 kbps it is about 1 MB per minute. At 64 kbps it is about half a megabyte, at 192 kbps about 1.4 MB and at 320 kbps about 2.4 MB per minute.

### Can I paste a YouTube link to get an MP3?

No. This tool only converts a file that is already on your device, and it does not download from web links. Convert only recordings you own or have permission to use.

### Why does my long video not convert?

The browser has to unpack the sound first, which takes about 21 MB per minute for stereo, and there is a 400 MB file limit. Trim the video into shorter pieces, close other tabs, and try again.

### Does the Mono option make the file smaller?

Not at a steady bitrate. The size is set by the kbps you pick. Mono mixes both channels into one, which suits speech. To get a smaller file, choose a lower kbps.

### Is it safe to convert a video to MP3 online?

It is safest when the video never leaves your device. The Video to MP3 tool works inside your browser, so your file is not uploaded.